1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to the art of preventing contamination of various components of the image forming apparatus due to waste toner.
2. Description of Related Art
An electrophotographic image forming apparatus is provided with a process unit that forms a toner image used as a printing image. In the process unit, to begin with, a charging portion charges the peripheral surface of a photoreceptor drum. The charged peripheral surface of the photoreceptor drum is irradiated with laser light, which forms an electrostatic latent image on the peripheral surface of the photoreceptor drum. Subsequently, a developing portion visualizes the electrostatic latent image and thus forms a toner image. The toner image is transferred onto a paper sheet for example through a transfer belt.
In the above apparatus, the charging portion has a wire, a saw-toothed electrode, or the like as an electrode that generates discharge necessary for the charging of the photoreceptor drum. On the other hand, if a stain is attached to such an electrode, the charging performance will be reduced. Therefore, a technique to clean an electrode has been proposed. For example, a technique in which a cleaning device is built in a process unit and cleaning is automated is proposed (see Japanese Unexamined Patent Application Publication No. 2012-185335, for example). In addition, as cleaning technique, cleaning is performed manually such that a cleaning tool is inserted into a charging portion from the outside of a process unit.
However, when the cleaning is performed manually, the process unit needs to be provided with an insertion port into which the cleaning tool is inserted. In other words, the charging portion of the process unit comes to communicate with the outside of the process unit through the insertion port.
On the other hand, in the process unit, the toner that remained on the peripheral surface of the photoreceptor drum after the toner image is transferred is collected and is discharged as waste toner to the outside of the process unit. Specifically, the process unit is provided with a discharge pipe for guiding the waste toner to the outside of the process unit, and the discharge pipe is drawn from the process unit and includes at a tip portion a discharge port for discharging the waste toner. The waste toner discharged from the discharge port falls down, and is supplied to a waste toner tank.
However, when the waste toner falls from the discharge port into the waste toner tank, air is blown out of the inlet port of the waste toner tank due to the influence of the waste toner. Therefore, a problem has occurred such that waste toner leaks out of the waste toner tank with the blown air. In addition, in order to make it easier to clean an electrode and perform maintenance such as replacement of a waste toner tank, the insertion port is, in many cases, provided on the same surface as the side surface of the process unit from which the discharge pipe is drawn. Therefore, the waste toner that has leaked out of the waste toner tank enters from the insertion port and, as a result, a problem that the electrode of the charging portion is contaminated has occurred.